Dual antenna

Abstract

 A dielectric dual antenna intended especially for small-sized radio devices, by one partial antenna of which is implemented the lower operating band of the antenna and by the other partial antenna the upper operating band. The partial antennas have a shared substrate (440), which together with the radiators constitutes an integrated antenna component (400). The partial antennas also have a shared feed point (FP), the part of the antenna component to one direction from the plane, which leads through the feed point and is perpendicular to the upper surface of the substrate, belonging to one partial antenna and the part of the antenna component to the opposite direction belonging to the other partial antenna. At least one of the partial antennas comprises two radiators, the first one (411) of which joins the feed point and the second one (412) is connected to the ground (GND) from its outer end as viewed from the first radiator. This first radiator (411) and the radiator (421) of the other partial antenna, which joins the shared feed point, form a unitary common element (430) on the substrate surface. This common element is shortcircuited to the ground from at least one point (SP1, SP2) relatively near to the feed point. The matching of the dual antenna can be improved in either operating band without degrading it in the other operating band at the same time.

Description

[0001] The invention relates to an antenna structure intended to small-sized radio apparatus which structure comprises two electrically relatively separate parts for implementing two operating bands.

[0002] In small-sized portable radio apparatuses, such as mobile phones, the antenna is placed for convenience of use preferably inside the covers of the apparatus. Furthermore, as one tries to make the antenna to consume as small a space as possible, its design becomes demanding. Additional difficulties in design are caused if the radio apparatus has to operate in several frequency ranges, the more the broader these ranges are.

[0003] Internal antennas are mostly plane-structured, in which case they comprise a radiating plane and a ground plane at a certain distance from it. A planar antenna can be made smaller by manufacturing the radiating plane on the surface of a dielectric substrate instead of it being air-insulated. The higher the permittivity of the material, the smaller, naturally, an antenna element with a certain electric size is physically. By using e.g. ceramics having a high dielectric constant as the substrate, the antenna component becomes a chip to be mounted on a circuit board. Fig. 1 shows an example of a dielectric antenna, or an antenna based on such a chip component. The structure is a dual antenna; it includes two antenna components with a ceramic substrate on the circuit board PCB of a radio device and the partial antennas corresponding to them. The antenna structure has a lower and an upper resonance, and it has correspondingly two bands: the lower operating band is implemented by the first antenna component 110, and the upper operating band by the second antenna component 120. On the surface of the substrate of the first antenna components there are two antenna elements with same size, between which elements remains a relatively narrow slot on the top surface of the substrate. The feed conductor of the partial antenna in question leads to one element, and the other element is a parasitic element connected to the ground GND and getting its feed electromagnetically over said slot. On the surface of the substrate of the second antenna component 120 there is in this case one antenna element, which is connected both to the feed conductor of the partial antenna in question and to the ground. There is no ground plane below the antenna components, and the ground plane beside them is at a certain distance from them to match the partial antennas.

[0004] Because of the separateness of the antenna components, also their electromagnetic near fields are separate, and the isolation between the partial antennas is good in this respect. The partial antennas have a shared feed conductor 131 connected to the antenna port AP of the radio apparatus, which conductor branches to feed conductors leading to the antenna components. If these feed conductor branches were connected directly to the radiating elements, the partial antennas would adversely affect each other via their shared feed so that the tuning of one would change the tuning of the other. Furthermore, the upper resonance would easily become weak or it would not excite at all. For this reason the structure requires matching components. In the example of Fig. 1, in series with the feed conductor of the first antenna component 110 there are a coil L1 and a capacitor C1. The natural frequency of the resonance circuit constituted by these is the same as the centre frequency of the lower operating band. In series with the feed conductor of the second antenna component 120 there is a capacitor C2, and between its end on the side of the antenna component and the ground plane GND there is a coil L2. The boundary frequency of the high-pass filter constituted by the capacitor C2 and the coil L2 is somewhat below the upper operating band.

[0005] A disadvantage of the solution according to Fig. 1 is the space required by the matching components on the circuit board and additional costs in production incurred by them. It is conceivable that the required matching is made without discrete components with conductor patterns on the surface of the circuit board, but in any case this kind of patterns would require a relatively large area on the circuit board.

[0006] Fig. 2 shows another example of a known dual antenna. There the partial antennas have a shared substrate 240, which together with the radiating elements constitutes an antenna component 200. Only this antenna component seen from above and sideways is presented in Fig. 2. Also the ground plane on the circuit board of the radio apparatus, on which the antenna component is mounted, belongs functionally to the antenna. The lower operating band of the whole antenna structure is implemented by the first partial antenna, and the upper operating band by the second partial antenna.

[0007] The substrate 240 is divided to the substrate of the first partial antenna, or the first partial substrate 241, and the substrate of the second partial antenna, or the second partial substrate 242. The partial substrates are here separated from each other by three holes HL1, HL2, HL3 extending vertically through the substrate and by two grooves CH1, CH2. The first groove CH1 is at the holes downwards from the top surface of the substrate and the second groove CH2 is at the holes upwards from the bottom surface of the substrate. Thus four relatively narrow necks remain to connect the partial substrates. In this way the electrical isolation and the matching possibilities of the partial antennas are improved.

[0008] The first partial antenna comprises the first 211 and second 212 radiating element. The first radiating element 211 covers one portion of the top surface of the partial substrate 241 and extends through said holes a bit on the side of the bottom surface of the substrate to constitute the contact pad 217. The first radiating element is connected to the feed conductor through that contact pad, which then is the shared feed point of the partial antennas. The second antenna element 212 covers another portion of the top surface of the partial substrate 241 and extends through its head surface a bit on the side of the bottom surface of the substrate to constitute the contact pads 219. The second radiating element is connected to the signal ground through these contact pads. The second radiating element is then parasitic; it gets its feed electromagnetically over the narrow slot between the elements. The second partial antenna comprises the third radiating element 221. This element covers at least partly the top surface and the outer head surface of the second partial substrate 242.

[0009] The second partial antenna gets its feed galvanically through the first radiating element 211 and an intermediate conductor 232. The intermediate conductor is located in this example on one side surface of the substrate 240, which is coated by conductor so that the opposing ends of the first and third radiating element become coupled to each other. In this case the intermediate conductor 232 has to go round the end of the first groove CH1 thus forming a U-shaped bend.

[0010] Because of the mutual position of the partial substrates, the main direction of the radiating elements of the first partial antenna and the main direction of the radiating element of the second partial antenna are opposing seen from the shared feed point. This improves from its part the electrical isolation and matching of the partial antennas.

[0011] A disadvantage of the above-described dual antenna solutions is that in them the matching of the antenna both in the lower and upper operating band requires arrangements, which increase the production costs, and nevertheless the result is not such as desired. The object of the invention is to implement a dual antenna, which minimises said disadvantage related to prior art. The dual antenna according to the invention is characterised by what is presented in the independent claim 1. Some advantageous embodiments of the invention are described in the other claims.

[0012] The basic idea of the invention is the following: The dielectric antenna is a dual antenna, by one partial antenna of which is implemented the lower operating band of the antenna and by the other partial antenna the upper operating band. The partial antennas have a shared substrate, which together with the radiators constitutes an integrated antenna component. The partial antennas also have a shared feed point, the part of the antenna component to one direction from the plane, which leads through the feed point and is perpendicular to the upper surface of the substrate, belonging to one partial antenna and the part of the antenna component to the opposite direction belonging to the other partial antenna. At least one of the partial antennas comprises two radiators, the first one of which joins the feed point and the second one is connected to the ground from its outer end as viewed from the first radiator. This first radiator and the radiator of the other partial antenna, which joins the shared feed point, form a unitary common element on the substrate surface. This common element is short-circuited to the ground from at least one point relatively near to the feed point.

[0013] An advantage of the invention is that an integrated dual antenna provided with a shared feed point can be matched relatively easily in its both operating bands. This is due to that the short-circuits near to the feed point in itself improve the total matching of the antenna and further enable an additional improvement of the matching by extra component in either operating band without degrading the matching in the other operating band at the same time. Relating to the matching improvement, the isolation between the partial antennas is good, although they have the shared substrate. Another advantage of the invention is that the efficiency of the antenna is good considering the size of the antenna.

[0014] The invention will now be described in detail. The description refers to the accompanying drawings in which

Fig. 1

shows an example of a known dielectric dual antenna,

Fig. 2

shows another example of a known dielectric dual antenna,

Fig. 3

shows an example of a dielectric dual antenna according to the invention,

Fig. 4

shows a second example of a dielectric dual antenna according to the invention,

Fig. 5

shows a third example of a dielectric dual antenna according to the invention,

Fig. 6

shows a fourth example of a dielectric dual antenna according to the invention,

Fig. 7

shows a fifth example of a dielectric dual antenna according to the invention,

Fig. 8

shows a sixth example of a dielectric dual antenna according to the invention,

Fig. 9

shows a seventh example of a dielectric dual antenna according to the invention,

Fig. 10

shows an eighth example of a dielectric dual antenna according to the invention,

Fig. 11

shows an example of a dielectric dual antenna according to the invention as mounted, and

Fig. 12

shows an example of the band characteristics of an antenna according to the invention.

[0015] Figs. 1 and 2 were already described in connection with the description of prior art.

[0016] Fig. 3 shows an example of a dielectric dual antenna according to the invention. There are the first partial antenna, by which the lower operating band of the whole antenna is implemented and the second partial antenna, by which its upper operating band is implemented. In the figure the antenna component 300 is seen from the front side as a perspective depiction and in the second partial figure from the back side. Also the ground plane on the circuit board of the radio apparatus, on which the antenna component is mounted, belongs functionally to the antenna. The integrated antenna component 300 comprises a substrate 340 shared between the partial antennas and the radiating elements of the antenna as conductor coatings of the substrate. The substrate 340 is here an elongated ceramic piece substantially shaped like a right-angled prism without any holes or grooves which would divide the piece. The number of the radiating elements is three in this example: the common element 330 according to the invention, the first end element 312 and the second end element 322.

[0017] On the front surface of the substrate there is a conductor strip FC belonging to the antenna feed conductor and joining galvanically the common element 330 at the feed point FP. The feed conductor FC and the feed point FP are shared between the partial antennas. The feed point functionally divides the antenna component into two parts so that starting from the substrate cross section which leads through the feed point, the part towards the first end element 312 belongs to the first partial antenna and the part of the antenna component to the opposite direction, or towards the second end element 322, belongs to the second partial antenna. The common element 330 functionally comprises two parts: the first radiator 311 of the first partial antenna and the first radiator 321 of the second partial antenna. In this case said first end element 312 is the second radiator of the first partial antenna and the second end element 322 is the second radiator of the second partial antenna. More briefly, the first radiator of the first partial antenna is only called the first radiator, the second radiator of the first partial antenna only the second radiator, the first radiator of the second partial antenna only the third radiator and the second radiator of the second partial antenna only the fourth radiator. Between the first 311 and second 312 radiator there is only a narrow slot travelling across the upper surface of the substrate, partly in its longitudinal direction, the second radiator receiving its feed electromagnetically over the slot. Seen from the feed point FP, the outer end of the first radiator 311 continues from the upper surface of the substrate, where the common element 330 mostly is located, to the front surface of the substrate. Correspondingly, the end of the second radiator 312 nearest to the feed point FP continues from the upper surface of the substrate to the back surface of the substrate. The second radiator covers also the first head surface of the substrate 340 and extends a little to its lower surface, where it connects to the signal ground, or ground plane GND, when the antenna component has been mounted. Correspondingly, in this example only a narrow slot travelling across the upper surface of the substrate is between the third 321 and fourth 322 radiator, the fourth radiator receiving its feed electromagnetically over this slot. The fourth radiator covers also the second head surface of the substrate and extends a little to its lower surface, where it connects to the ground plane, when the antenna component has been mounted. By means of this kind of radiator structures together with the ceramic substrate the antenna can be made in very small size.

[0018] According to the invention, the common element 330 is also connected to the ground plane GND from the short-circuit point SP, which is located opposite the feed point FP on the other edge of the upper surface of the substrate. Thus the distance between the short-circuit and feed points is about the width of the substrate, which is relatively small compared with the length of the substrate. The ground connection of the common element is implemented by the short-circuit conductor SC, which is located on the back surface of the substrate opposite the feed conductor FC viewed in the transverse direction of the substrate and extends a little to its lower surface for constituting a contact surface. The total matching of the antenna can be improved by means of such a short-circuit relatively close to the feed point, especially together with a matching component connected to the feed conductor.

[0019] The prefixes 'upper', 'lower', 'front' and 'back' are defined in this description and claims just on grounds of the location of the parts of the radiating conductor. So the lower surface of the substrate means its surface, coating of which is substantially only relatively small contact surfaces for mounting the antenna component, and the front surface means the surface, on which the feed conductor FC is located. The use position of the antenna component can naturally be any. 'The first head' means the head on the side of the first end element, and 'the second head' means naturally the opposite head in respect of the first head.

[0020] Fig. 4 shows a second example of the dielectric dual antenna according to the invention. In the figure the antenna component 400 is seen from the front side as a perspective depiction and in the second partial figure from below. The antenna component comprises a substrate 440 shared between the partial antennas and the radiating elements of the antenna as conductor coatings of the substrate. The substrate 440 is also in this example an elongated ceramic piece shaped substantially like a right-angled prism, and on its surface there are the common element 430, the first end element 412 and the second end element 422 as in Fig. 3. The substantial difference to the structure shown in Fig. 3 is that there are now two short-circuit conductors of the common element instead of one, and these both conductors are located on the front surface of the substrate. A little from the feed point FP towards the first head of the substrate there is the first short-circuit point SP1, which is connected to the ground plane GND by the first short-circuit conductor SC1 next to the feed conductor FC. A little from the feed point FP towards the second head there is the second short-circuit point SP2, which is connected to the ground plane by the second short-circuit conductor SC2 on the other side of the feed conductor.

[0021] By means of two short-circuits close to the feed point the antenna impedances on the lower and upper operating band can be set so that a further improvement of the matching by an extra component in either operating band does not degrade the matching in the other operating band at the same time.

[0022] Fig. 5 shows a third example of the dielectric dual antenna according to the invention. In the figure the antenna component 500 is seen from the front side as a perspective depiction. The antenna component comprises a substrate 540 shared between the partial antennas and the radiating elements of the antenna as conductor coatings of the substrate. On the surface of the substrate there are the common element 530 and the first end element 512 as in Figs. 3 and 4. The difference to the structure shown in those figures is that the second partial antenna now comprises only one radiator 520 which, together with the first radiator like the one in the foregoing examples, constitutes said common element 530. The radiator 520 of the second partial antenna, or the third radiator, covers the upper surface of the substrate 540 on the side of the second head and can extend to the second head surface, but not there from onwards to the ground plane, being then open at its outer end. The common element has in this example one short-circuit conductor SC, which is located on the front surface of the substrate next to the feed conductor FC on the side of the second head. For this short-circuit conductor the second partial antenna can be considered to be of PIFA type, if the antenna ground plane is extended below the third radiator 520. The same short-circuit also effects on the matching of the first partial antenna at the same time.

[0023] Fig. 6 shows a fourth example of the dielectric dual antenna according to the invention. There the second partial antenna comprises only one radiator 620, which is not grounded from its outer end, as in the example of Fig. 5. The difference to the structure shown in Fig. 5 is that the third radiator 620 now is meander-shaped. In addition, now the short-circuit conductor SC of the common element 630 is located on the side of the first head in respect of the feed conductor FC.

[0024] Fig. 7 shows a fifth example of the dielectric dual antenna according to the invention. In the figure the antenna component 700 is seen from the back side as a perspective depiction. The common element 730 belonging to it comprises two short-circuit points and conductors, as in Fig. 4, but now the second short-circuit conductor SC2 is located on the back surface of the substrate 740, the first short-circuit conductor being located on the front surface of the substrate next to the feed conductor. An additional difference to the structure shown in Fig. 4 is that now the second radiator 712 of the first partial antenna is mostly located on the back surface of the substrate. It covers also the first head surface of the substrate so that the slot between the first 711 and second 712 radiator travels across the upper surface of the substrate close to the first head and continues then along the upper edge of the back surface towards the second head. Here the first radiator 711 is wholly located on the upper surface of the substrate.

[0025] Fig. 8 shows a sixth example of the dielectric dual antenna according to the invention. In the figure the antenna component 800 is seen from the back side as a perspective depiction and in the second partial figure from below. There the common element 830 has a single short-circuit conductor and this conductor is located on the front surface of the substrate 840 next to the feed conductor. Here the common element continues from the upper surface of the substrate to the back surface on the area, which extends in the longitudinal direction from the point opposite to the feed point FP near to the second head. In this case especially the first radiator 821 of the second partial antenna extends also to the back surface. Also a part of the second radiator 822 of the second partial antenna is located on the back surface, the large part of it being located on the upper surface and the second head surface. The first 811 and second 812 radiator of the first partial antenna are located so that the slot between them on the upper surface of the substrate starts on the side of the front surface close to the feed point FP, travels longitudinally in the middle of the upper surface to a point relatively close to the first head and turns after that sideways towards the back surface. The second radiator 812 can extend from the upper surface also on the side of the front surface.

[0026] Fig. 9 shows a seventh example of the dielectric dual antenna according to the invention. In the figure the antenna component 900 is seen from the front side as a perspective depiction. There are a short-circuit conductor on both sides of the feed conductor FC, as in Fig. 4. The difference to the structure shown in Fig. 4 is that now the slot 925 between the radiators 921, 922 of the second partial antenna is located on the second head surface instead of the upper surface. At the other edge of the common element 930, the slot between the radiators 911, 912 of the first partial antenna starts here on the side of the front surface close to the first head and travels diagonally across the upper surface to the side of the back surface close to the second head.

[0027] Fig. 10 shows an eighth example of the dielectric dual antenna according to the invention. Seen from above, the substrate of the antenna component A00 is in this example a rounded plate so that its front surface, back surface and head surfaces all have roughly the same size. Parallelly at a place on the front surface there are the antenna feed conductor FC and the short-circuit conductor SC of the common element A30. Also in this case the slot A15 between the radiators A11, A12 of the first partial antenna and the slot A25 between the radiators A21, A22 of the second partial antenna make boundaries of the common element. The former slot makes a curved line across the upper surface of the substrate from the side of the first head surface to the side of the back surface, and the latter slot A25 travels across the upper surface of the substrate from the side of the front surface to the border area of the back surface and the second head surface. One radiator of both partial antennas are intended to be connected to the ground from their outer edge, seen from the common element A30.

[0028] Fig. 11 shows an example of a dielectric dual antenna according to the invention as mounted. A part of the circuit board PCB of a radio device is seen in the figure, the upper surface of the board largely being of conductive ground plane. In this example the antenna component B00 has been fastened from its lower surface to the circuit board close to its one end. The feed conductor FC on the front surface of the antenna component continues on the circuit board as a conductor FC'. Between this conductor FC' and the signal ground there is connected the reactive matching component B50 of the antenna. In addition to the design of the antenna component itself, the antenna impedances in the operating bands naturally depend on several factors such as the size of the circuit board, the place of the antenna component on the circuit board, the shape of the ground plane and the other conductive parts of the device. Depending on the case, the matchings can succeed also without a discrete matching component. The edge of the ground plane GND is in the example of Fig. 11 at a certain distance from the antenna component B00 in its transverse direction. That distance is a variable in the antenna design. The antenna can be designed also so that the ground plane extends at least partially below the antenna component.

[0029] Fig. 12 shows an example of the band characteristics of an antenna according to the invention. The curve shows the fluctuation of the reflection coefficient S11 as a function of frequency. The lower reflection coefficient, the better the antenna has been matched and the better it functions as a radiator and a receiver of radiation. The antenna has been designed so that its lower operating band covers the narrow range at the frequency 1575 MHz used by the GPS (Global Positioning System). The upper operating band again well covers the frequency range used by the WLAN system (Wireless Local Area Network), which range is 2400-2484 MHz in the EU countries and the USA. Correspondingly the antenna could be designed so that the lower operating band would cover e.g. the frequency range used by the GSM900 system and the upper operating band cover e.g. the frequency range used by the GSM1800 system.

[0030] The efficiency of the antenna according to the invention is good especially in the upper operating band considering the small size (for example 15mm-3mm-4mm) of the antenna. In the free space the efficiency is typically about 50% in the lower operating band and about 60-70% in the upper operating band.

[0031] An antenna according to the invention can naturally differ in its details from the ones described. The shapes of the radiating elements can vary also in other ways than what appears from the examples. Also the shape of the substrate can vary. The places of the short-circuits of the common element can vary regardless of the number and shapes of the radiators. The substrate can be instead of ceramic, also of other dielectric material, as pure silicon. In this case the antenna is manufactured by growing a metal layer on the surface of the silicon and removing a portion of it with a technology used in manufacturing of semiconductor components. The inventive idea can be applied in different ways within the limitations set by the independent claim 1.

Claims

1. A dual antenna of a radio device comprising a first partial antenna to implement a lower operating band of the antenna and a second partial antenna to implement an upper operating band, which partial antennas have a shared dielectric substrate (340; 440; 540; 640; 740; 840; 940; A40) which constitutes an integrated antenna component (300; 400; 500; 600; 700; 800; 900; A00; B00) together with antenna radiators, the partial antennas having a shared feed point (FP) and a shared feed conductor (FC) on the front surface of the substrate, and a part of the antenna component to one direction from a substrate cross section which leads through the feed point belongs to the first partial antenna and a part of the antenna component to the opposite direction belongs to the second partial antenna, and at least one partial antenna comprises two radiators, the first (311; 411; 511; 611; 711; 811; 911; A11) of which joins galvanically the feed point (FP) and the second (312; 412; 512; 612; 712; 812; 912; A12) of which is intended to be connected to a ground plane (GND) from its outer end seen from the first radiator, characterised in that said first radiator (311; 411; 511; 611; 711; 811; 911; A11) and a radiator (321; 421; 520; 620; 721; 821; 921; A21) of the other partial antenna joining the shared feed point (FP) form a unitary common element (330; 430; 530; 630; 730; 830; 930; A30) on the upper surface of the substrate, which element is intended to be connected to the ground plane (GND) from at least one short-circuit point (SP; SP1, SP2) relatively close to the feed point compared with the longest dimension of the antenna component.

2. A dual antenna according to claim 1, characterised in that there is only one said short-circuit point (SP) of the common element (330), and a short-circuit conductor (SC) starting from that point is located on back surface of the substrate opposite the feed conductor (FC) seen in the transverse direction of the substrate.

3. A dual antenna according to claim 1, characterised in that there is only one said short-circuit point (SP) of the common element (530; 630; 830), and a short-circuit conductor (SC) starting from that point is located on the front surface of the substrate on either side of the feed conductor (FC).

4. A dual antenna according to claim 1, characterised in that the number of said short-circuit points of the common element (430; 930) is two, and a first short-circuit conductor (SC1) starting from first short-circuit point (SP1) is located on the front surface of the substrate on one side of the feed conductor (FC) and a second short-circuit conductor (SC2) starting from second short-circuit point (SP2) is located on the front surface of the substrate on the other side of the feed conductor (FC).

5. A dual antenna according to claim 1, characterised in that the number of said short-circuit points of the common element (730) is two, and a first short-circuit conductor starting from first short-circuit point (SP1) is located on the front surface of the substrate next to the feed conductor and a second short-circuit conductor (SC2) starting from second short-circuit point (SP2) is located on the back surface of the substrate opposite the feed conductor seen in the transverse direction of the substrate.

6. A dual antenna according to claim 1, characterised in that said partial antenna, the first radiator of which joins galvanically the feed point (FP) and the second radiator of which is intended to be connected to the ground plane (GND) from its outer end seen from the first radiator, is the first partial antenna of the dual antenna, and its first (311; 411; 511; 611; 711; 811; 911) and second (312; 412; 512; 612; 712; 812; 912) radiator are separated from each other by a relatively narrow slot, and said second radiator extends through a first head surface of the substrate (340; 440; 540; 640; 740; 840; 940) to a lower surface of the substrate, where it connects to the ground plane (GND) when the antenna component has been mounted.

7. A dual antenna according to claim 6, characterised in that the first radiator (411; 511; 611; 711; 911) of the first partial antenna is substantially wholly located on the upper surface of the substrate (440; 540; 640; 740; 940).

8. A dual antenna according to claim 6, characterised in that at least one of the radiators (311, 312; 811, 812) of the first partial antenna extends from the upper surface of the substrate (340; 840) to its front or back surface.

9. A dual antenna according to claim 8, characterised in that the second radiator (712) of the first partial antenna is mostly located on the back surface of the substrate (740).

10. A dual antenna according to claim 6, characterised in that also the second partial antenna comprises two radiators separated from each other by a relatively narrow slot, a first radiator (321; 421; 721; 821; 921) of which joins galvanically the feed point (FP) and a second radiator (322; 422; 722; 822; 922) of the second partial antenna extends through a second head surface of the substrate to the lower surface of the substrate, where it connects to the ground plane, when the antenna component has been mounted.

11. A dual antenna according to claim 10, characterised in that the slot between the first and second radiator of the second partial antenna is substantially wholly located on the upper surface of the substrate (340; 440; 740).

12. A dual antenna according to claim 10, characterised in that the first (821) and second (822) radiator of the second partial antenna and the slot between these radiators extend from the upper surface of the substrate (840) to its back surface.

13. A dual antenna according to claim 10, characterised in that the slot (925) between the first and second radiator of the second partial antenna is located on the second head surface of the substrate (940).

14. A dual antenna according to claim 6, characterised in that the second partial antenna comprises only one radiator (520; 620), which covers at least a part of the upper surface of the substrate on the side of its second head and is open at its outer end.

15. A dual antenna according to claim 14, characterised in that the radiator (620) of the second partial antenna is meander-shaped.

16. A dual antenna according to claim 1, characterised in that it further comprises a reactive matching component (B50), which is connected between the antenna feed conductor (FC, FC') and the signal ground (GND).

17. A dual antenna according to claim 1, characterised in that said substrate is of ceramic material.

18. A dual antenna according to claim 1, characterised in that the edge of the ground plane (GND) is at a certain distance from the antenna component (B00) in the transverse direction of that component.

19. A dual antenna according to claim 1, characterised in that the ground plane extends below the antenna component at least partly.

Drawing